Pipes are used to transport fluids of all sorts. Because the measurement of these fluids is important, various types of fluid measuring devices such as orifice plates, flow meters, turbine meters, etc. are installed in-line with pipe sections. The use of such a measurement for flow has been known since ancient times.
The present invention relates in general to turbine flow meters. Turbine flow meters usually include a measuring chamber having a flow guide in the front of such chamber, a measuring wheel supported for rotation in the chamber and includes a magnetic device which counts the blade turnings for blades mounted on the hub of the measuring wheel.
The basic theory with regard to electronic turbine meters is that fluid flow through the meter impinges upon the turbine blades which are free to rotate about an axis along the center line of the turbine housing. The angular (rotational) velocity of the turbine rotor is directly proportional to the fluid velocity through the turbine. The output of the turbine meter is measured by an electrical pickup mounted in the meter body. The output frequency of this electrical pickup is proportional to the flow rate. Also, each electrical pulse is proportional to a small incremental volume of flow. This incremental output is digital in form, and as such, can be totalized with a maximum error of one pulse regardless of the volume measured.
Problems with existing turbine meters include a shift in the meter factor (K) curve over pressure change, rangeability over a large range of pressures, large size, and the intrusion of dirt.
It is an object of the present invention to avoid the meter factor curve change over the operating pressure of the meter, to permit high flow rangeability over a large range of pressure, such as substantially ambient to 1500 p.s.i. It is a further object of the present invention to substantially reduce the size of the meter. An additional object of the present invention is to inhibit intrusion of dirt within the mechanism of the measuring wheels supported for rotation in the chamber.